BE ALERT: Is fungicide resistance coming to your vineyard? Suzanne McKay Barbara Hall SARDI

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1 BE ALERT: Is fungicide resistance coming to your vineyard? Suzanne McKay Barbara Hall SARDI

2 Why do you think you may have resistance? Fungicide not working

3 Possible causes? Coverage Fungicide choice Correct rate Application timing Resistance

4 How does resistance develop? DNA mutations affect fungicide activity Sensitive: no mutation Resistant: naturally occurring mutation fungicide fungicide cells survive & reproduce Initial population Resistant population Adapted from GWDC/AWRI fact sheet

5 DNA mutations in fungal cells fitness Fungus life cycle Reproduction rate Environment Fungicide mode of action Resistance Fungicide rate coverage number timing

6 Testing for resistance Methods Botrytis Powdery & downy Sensitive OR Resistant? + Detect mutation(s) Lab tests for sensitivity

7 Resistance detected powdery mildew pyraclostrobin (Cabrio gp 11) 53% penconazole (Topas gp 3) 0 myclobutanil (Mycloss Xtra TM gp 3) 14% tetraconazole (Domark gp 3) 0

8 Resistance detected - Botrytis iprodione (Rovral gp 2) 28% pyrimethanil (Scala gp 9) 38% fenhexamid (Teldor gp 17) 7% boscalid (Filan gp 7) 21% azoxystrobin (Amistar gp 11) 5%* fludioxonil (gp 12) 0%* L. Harper and F. Lopez, Curtin Uni, WA * Only small numbers of samples tested

9 Resistance detected - Botrytis Modes of action (MOA) % of samples with reduced sensitivity 1 MOA 21% 2 MOA 11% 3 MOA 11% 4 MOA 3% (1 site each in SA & Vic) **54% of all sites sensitive L. Harper and F. Lopez, Curtin Uni, WA

10 Resistance detected - Downy Metalaxyl (gp 4): 67% resistant Mandipropamid (gp 40): 1 sample reduced sensitivity QoIs (gp 11): 1 sample reduced sensitivity Limited samples testing ongoing S. Savocchia, CSU

11 Fungicide resistance in Australian viticulture Botrytis Downy mildew Powdery mildew iprodione (2) metalaxyl (4) QoI (11) anilinopyrimidines (9) DMI (3) / DMI (3) QoI (11) fenhexamid (17) Carboxylic acid amides (CAA) (40) metrafenone (U8) boscalid SDHI (7) QoI (11) SDHI (7)* azanaphthalenes (13)* fludioxonil (12) phosphonates (33) spiroxamine (5) Red = resistance detected Green = not detected Black = not tested Purple = possible more testing needed * Limited numbers tested cyflufenamid (U6)

12 Issue to be solved: Relationship between: phenotypic testing (growing on fungicide treated leaf material) genotypic testing (molecular test for mutation) Botrytis good Powdery poor Downy??

13 EC 50 values for B. cinerea isolates against iprodione: Average EC 50 values (µg/ml) Bos 1 Bc 7 I365 Bc 38 I365 Bc 39 I365S Bc 40 Q369P, N373S Bc 98 I365S Bc 99 I365S good Isolates Phenotype = genotype Molecular test good but expensive L. Harper and F. Lopez, Curtin Uni, WA

14 EC 50 values for PM isolates against penconazole (Topas ): poor wild type 0.8 Y136F 0.6 not tested yet EC50 µg/ml 80a 59bulk 32a 44bulk 62a 40a 53a 94a 70a 85a 37bulk 33a 15a 30a 35a 57a 92a 108b 16b 27a 50a 93a 77a 25a ID1 TW1 91a 34b 76a 64a 100a 12a 29bulk 67a 28a 78a 86a TW2 89a 90a 36bulk 58a 75a 79a 17bulk sample (n= 45) Phenotype genotype Molecular test not able to be used yet

15 Powdery mildew Reduced sensitivity Mutant present pyraclostrobin (Cabrio gp 11) 53% 86% penconazole (Topas gp 3) 0 68% myclobutanil (Mycloss Xtra TM gp 3) 14% 84% tetraconazole (Domark gp 3) 0 82% Poor link between mutant & reduced sensitivity. Why? DMI mutation is a precursor for resistance

16 Issue to be solved: Relationship between: Lab results how many samples? Field performance what level failure? Botrytis some known Powdery unknown Downy??

17 Botrytis - dicarboximide 100% 90% 80% Percent samples with resistance 70% 60% 50% 40% 30% NZ 20% 10% France 0% Year of test

18 Result summary - Botrytis 46% of all sampling sites tested have some degree of resistance 20% of all isolates tested have some degree of resistance L. Harper and F. Lopez, Curtin Uni, WA

19 Population studies Resistance gene frequency% - 4 vineyards How many samples are needed? Distribution of resistance in a block? Issues Consistency of sample collection

20 Where are we now with testing? Botrytis: Relationship between lab test and field performance known for older fungicides Good relationship between phenotypic and genotypic tests Potential for in field testing eg LAMP assays Commercial testing available (plate assays) Powdery mildew: Phenotypic tests work but laborious and sample size needed unknown Relationship between phenotypic and genotypic tests not clear Commercial testing not available Downy mildew: Phenotypic tests work but consistency of results an issue Metalaxyl has no known mutation Commercial testing not available

21 New research Link between laboratory results and field failure Intensive monitoring needed, link with sprays & field efficacy How many samples? Other mutations or genetic causes? Understanding differences among DMIs Which DMI is best to use? Fitness of resistant populations When can you reintroduce that chemistry again? Regional resistance monitoring - non-biased sampling Spore trapping technologies Powdery sensitivity to other fungicide groups Quick, reliable in-field test for resistance

22 Manage poor performance Good coverage Fungicide choice Correct rate Timing Manage resistance risk

23 Managing resistance risk Always follow resistance management guidelines Rotate or mix different modes of action Use label rates Limit total number of applications per fungicide group Educate yourself about fungicide activity, modes of action, resistance groups & management practices Start a fungicide program with a multi-site MOA to reduce populations DO NOT use single-site MOA to control wellestablished infections UC Davis

24 Thanks to Wine Australia, growers & viticulturists Project team & industry collaborators Industry reference group Vitisolutions